The polyphenylene oxides and methods for their preparation are known in the art and are described in numerous publications, including Hay U.S. Pat. No. 3,306,874 and U.S. Pat. No. 3,306,875. The Hay processes are based on the use of copper-amine complexes. Manganese catalyzed methods for the preparation of polyphenylene oxides are disclosed in McNelis, U.S. Pat. No. 3,220,979; Olander, U.S. Pat. No. 3,956,242; Nakashio, U.S. Pat. No. 3,573,257; and Nakashio, U.S. Pat. No. 3,787,361.
In the applicant's copending applications Ser. No. 491,370, filed July 24, 1974 and Ser. No. 534,903, filed Dec. 20, 1974, there are disclosed novel procedures for polymerizing polyphenylene oxides with complex manganese based catalysts. All of these patents and applications are hereby incorporated by reference.
The procedures employing manganese based catalysts have been based on the oxidative coupling of a phenolic monomer in an appropriate organic solvent. The manganese chelate catalyst is not a self limiting catalyst system and a need has existed for a method which permits precise control of the build stage of the polymerization reaction. The control of the rate of reaction during build stage is important as this can affect the physical properties of articles molded from the polymer. It has now been found that the addition of a polyfunctional alkanolamine at a particular stage of the reaction will provide a means for gradual polymer build over a period of time that does not result in an unduly extended polymerization cycle. The polyfunctional alkanolamines are preferably added when the polyphenylene oxide polymer reaches a I.V. of about 0.2 dl/g as measured in chloroform at 30.degree. C. The use of the polyfunctional alkanolamines is also useful in reliably obtaining polyphenylene oxides of a desired range of intrinsic viscosities when the polymerization is carried out in a pressurized reactor.
In the prior art, ethanolamine, diethanolamine and triethanolamine have been employed as a polyphenylene oxide catalyst component that is complexed with the manganese salt prior to the initiation of the polymerization reaction. Examples of these processes are described in U.S. Pat. No. 3,787,361 and in Komoto et al, Die Makromolekulare Chemie 166 (1973) pp 57-58. These processes fail to suggest that polyfunctional alkanolamines will produce a moderating effect when added to a polyphenylene oxide polymerization reaction after the initial stages of the polymerization reaction have been completed.
Accordingly, it is a primary object of this invention to provide a means for retarding the rate of oxidative coupling in a polyphenylene oxide polymerization reaction which permits the regulation of the build stage of polymerization.
It is also a further object of this invention to provide a method for making manganese chelate catalyzed polymerization of phenolic monomers self-limiting with regard to the final intrinsic viscosity of the polymer.